I don't really get this sentiment. I don't really see too many Leafs fans saying "OMG top pairing PPQB ROFLOL" or anything. Most have now had a couple chances to see him on the Marlies and know what he brings. It's nice to have a prospect who can rush the puck and make outlet passes without crapping the bed. One who can apparently play good defense at the pro level already. Beyond that I don't think there's much expectation for big numbers.
...and this is what we needed after the Kaberle trade - a guy talented enough to play an offensive role comfortably within top-four minutes, preferably alongside Schenn, who was Kaberle's defensive-partner, and Gardiner as a left-hander is ideal. Gunnarsson is a solid two-way guy, but he's not so offensively inclined to compensate for the loss of Kaberle. Phaneuf, returning to form, is still our only legitimate offensive defenseman, so what we need is another guy to play such a role, especially on the powerplay where we especially lack that talent, Lashoff being given minutes lately. It would be great to have instead a guy who is certainly more overtly talented, such as a Fowler, but I am at least happy with a guy who seems to have enough talent to play a legitimate top-four offensive role, as a PPG college player and first-round pick, and seemingly no huge flaws in his game, although no huge upside. Gardiner is a good top-four offensive defenseman prospect, and that's what we need. If ultimately the guy can put up 30-35 points while playing the second powerplay unit and consistently leading the rush up ice while also playing a reasonable defensive game, then this guy is worth it. A guy like McDonagh may even have outperformed Gardiner to an extent, but a guy like that is playing a more defensive role. Gardiner is a more valuable prospect.